The detection and evaluation of defects within various non-metallic materials by non-destructive use of radiation is generally known in the art, including use of microwave radiation exhibiting certain advantages over other forms of radiation such as x-ray, ultrasound and thermography radiation. Such prior art use of microwave radiation include emission and back-scattering of the emitted radiation after interaction with the targeted material for detecting the presence or absence of a defect therein. Microwave radiation types of defect detection systems heretofore involved one or more antennas for emission of the radiation and reception of reflective back-scattering thereof. Some of the advantages over the use of other forms of radiation include, avoiding use of a couplant and heat diffusion means, increasing depth of detection and avoiding the provision of radiation hazard prevention. It is therefore an important object of the present invention to enlarge evaluation of defects in non-metallic materials by the advantageous use of microwave radiation.